In conventional semiconductor devices that use a commonly used silicon (Si) semiconductor element, an epoxy resin and a silicone gel are used for sealing to secure the insulating properties. On the other hand, because SiC and GaN have electrical characteristics superior to those of Si, research and development of SiC and GaN have been conducted in recent years to commercialize semiconductor devices that use these materials. It is assumed that the material of semiconductor elements will be changed from Si to SiC and GaN in the future. Semiconductor elements constituted by SiC and GaN have high-temperature operation characteristics superior to those of Si semiconductor elements. It has been considered that SiC, in particular, is capable of operating at a temperature up to 300° C.
If SiC is used in a semiconductor element, the current density of the semiconductor element can be increased, but if the current density of a semiconductor element is high, the heat generation may increase and the temperature of the semiconductor element may become high. Accordingly, it is necessary to increase the heat performance of a sealing material to be used. If a silicone gel commonly used in conventional techniques is used as the sealing material, the silicone gel may degrade by oxidative degradation at a high temperature of 175° C. or more and under an oxygen atmosphere, which may lead to cracks in some cases. In addition, similarly to the above case, if a common epoxy resin is used as a sealing material, the resin may be oxidatively degraded and the problem of cracks may occur.
Self-repairing methods for repairing cracks in general plastic materials has been known. For example, JP 2008-052810 discloses fiber-reinforced plastic in which a plurality of capsule bodies encapsulating an adhesive is embedded. In addition, JP 2007-040491 discloses a laminated structure including a capsule filled with an adhesive and arranged between laminates of the laminated structure.
In semiconductor devices, a problem may occur such that if a crack has occurred in a sealing material such as an epoxy resin, the crack may develop and finally, cracks and peeling may occur in portions that need to be insulated.